In a DC circuit, the energy travels through the circuit primarily as the kinetic energy of the moving electrons. The capacitor, where the electrons may not actually cross from one plate to another, is an exception. There the electric force of one electron, arriving at a plate, pushes an electron off the other plate. That, of course, causes the first electron to stop and the second to move so the electrical force has transfered the kinetic energy from one electron to the other.